Catalyst solubilizing agents



States atent fifice 3,308,105 Patented Mar. 7, 1967 3,308,105 CATALYSTSOLUBILIZIN G AGENTS John M. Hoyt, Cincinnati, Ohio, Thomas B. Junas,Marlboro, Mass, and Lou Cornelia Key, Mount Airy, Ohio, assignors toNational Distillers and Chemical Corporation, New York, N.Y., acorporation of Virginia No Drawing. Filed Jan. 16, 1963, Ser. No.251,727

18 Claims. (Cl. 260-88.2)

This invention relates to a method of removing ash from low pressurehydrocarbon polymers. More particularly it relates to a process of thisnature utilizing a small amount of a phosphorus ester.

It is well known in the art to polymerize and copolymerize olefins anddiolefins at low pressures with catalyst systems containing a partiallyreduced, heavy transistion metal halide and a reducing metal-containingcompound. In general, these catalyst systems are of the Ziegler-typewhich comprise, in combination, (I) a reducing agent (generally called acocatalyst) as, for example, an element from Groups IA, HA, and IIIA,inclusive, of the Periodic Table (Handbook of Chemistry and Physics,42nd ed., 1960, pp. 448-449, Chemical Rubber), a metal alkyl, a metalalkyl hydride, a metal alkyl halide, mixtures thereof, etc., and (II) ahalide of a transition metal from Groups IVB, VB and VIB, inclusive, ofthe Periodic Table. The combination catalyst is generally used in anamount of from about 0.01 to about 2.0 weight percent, based on theweight of the monomeric reactant subjected to the polymerization, orcopolymerization; and regarding the relative proportions of the reducingagent to the transition metal halide in the combination catalyst, saidcatalyst generally comprises, in mole ratio, one mole of the transitionmetal halide to from about 0.5 to about moles of the reducing agent.

In further reference to the Ziegler-type catalyst, specific examples ofthe cocatalyst component (reducing agent) include the elements such assodium, lithium, magnesium aluminum, zinc, etc.; metal alkyls such astriethylaluminum, triisobutylaluminum, dibutylmagnesium, dibutylcadmium,diethylzinc, n-butyllithium; metal alkyl hydrides such asdiethylaluminum hydride, butylmagnesium hydride, including such hydridesnormally present in aluminum alkyls; and metal alkyl halides such as thesesquichlorides (mixtures of alkylaluminumdichloride anddialkylaluminumchloride), diethylaluminum chloride, butylmagnesiumchloride, dibutylaluminum iodide, and others.

The other component of the combination catalyst, namely ahalide-containing compound of the aforesaid transition metals, isgenerally a chloride thereof, although other halides such as thebromides, iodides, etc. may be used. Of such metals, the halides oftitanium, vanadium and molybdenum are preferred, but halides of othermetals such as those of niobium, zirconium, tungsten, and others, may beused. More specific examples of halides of the aforesaid transitionmetals useful for practice of this invention include VCl TiCl VOCl TiClNbCl MoO Cl and mixtures thereof,

More specific examples of the combination catalyst embodied for useherein include vanadium tetrachloride with triethylaluminum, andtitanium trichloride with triethylaluminum.

Although the Ziegler-type catalysts embodied for use herein comprise areducing agent and a halidecontaining compound of the aforesaidtransition metal, such catalysts can also contain additionalingredients. Thus, for example, such catalysts may contain a combinationof a halide of such a transition metal and an oxyhalide of the aforesaidtransition metals (e.g., VoCl and, in further example, in combinationwith vanadium tetrachloride or titanium tetrachloride along with areducing agent (e.g., trialkylaluminum) The alpha olefin feeds utilizedin polymerization and copolymerization include ethylene, propylene,butene-l, heptene-l, dodecene-l, etc., with ethylene and propylenepreferred. Diolefins which can be used in copolymerization includebutadiene, isoprene, piperylene, vinylcyclohexene, cyclopentadiene,1,4-pentadiene, etc. It is to be understood that the term polymer asused herein includes both homoand copolymers.

One of the problems associated with the use of the above-describedcatalyst systems is the ash introduced into the polymer from themetal-bearing catalyst components. While the ash content is dependentupon the catalyst efficiency, it generally ranges from about 1 to 3 wt.percent as determined by an ignition technique (dry ash). At theselevels, it tends to impart undesirable color and corrosivity behavior inthe polymer during subsequent processing and use.

In carrying out a polymerization using these catalyst systems, themonomers are generally contacted with the catalyst in the presence of aninert hydrocarbon diluent such as decalin, heptane, hexane, isopentane,benzene, and the like. The polymerization temperature ranges from about0 to 250 C.; the polymerization pressure ranges from about 0 to 5000p.s.i.g., usually 0 to 3000 p.s.i.g. The catalyst concentration in thepolymerization zone is preferably in the range of about 0.1 to 0.5 wt.percent based on total liquid and the polymer concentration in thepolymerization zone is preferably maintained between about 2 to 20%based on total contents so as to allow easy handling of the polymerizedmixture. When the desired degree of polymerization has been reached, anonsolvent for the polymer, e.g., methanol, ethanol, n-pro panol,isopropanol, butanol, and the like, can be added to the reaction mixtureto precipitate the polymer from solution. Such a precipitated polymergenerally retains undesirable quantities of catalyst residues asreflected by a high ash value. Alternatively, a solvent for the catalystcan be contacted with the polymer under such conditions of elevatedtempertaure and pressure that a homogeneous solution of polymer, polymersolvent, catalyst solvent, and solubilized catalyst results, and thesolubilized catalyst then removed by adsorption on a solid adsorbentsuch as silica or alumina.

One object of this invention is to provide a novel and effective agentfor removing ash from polymers.

Another object of this invention is to provide a novel and effectivemethod for removing ash from polymers produced by means of Ziegler-typecatalysts.

Other objects will become apparent from the ensuing description of theinvention;

It has now been found that a metal-bearing catalyst residue can beeffectively removed from a low pressure hydrocarbon polymer bycontacting said polymer containing said residue with a selected class ofphosphorus esters used in sufficient quantity to solubilize themetalbearing residue and thereafter separating the solubilizedmetal-bearing residue from the polymer.

The phosphorus esthers especially suitable for practice of thisinvention are characterized by the formula:

wherein R may be an alkyl radical of from about 1 to 20 carbon atoms oran aryl radical, R may be hydrogen or an alkyl radical of from about 1to 20 carbon atoms or an aryl radical, and X may be hydrogen or ahydroxyl radical. Preferably, R is an alkyl or aryl radical of fromabout 6 to 10 carbon atoms and R is hydrogen or an alkyl or aryl radicalof from about 6 to 10 carbon atoms. Included are dialkyl hydrogenphosphites such as his (2-ethylhexyl) hydrogen phosphite, diisooctylhydrogen phosphite, dialauryl hydrogen phosphite, distearyl hydrogenphosphite, and diphenyl hydrogen phosphite, as well as organic monoanddialkyl acid orthophosphates such as monoand di-(Z-ethylhexyl) acidorthophosphate, monoand diisooctyl acid orthophosphate, monoanddistearyl acid orthophosphate, and monoand diphenyl acid orthophosphate,and mixtures thereof, particularly mixtures of the monoand dialkylesters derived from the same alcohol. Particularly preferred compoundsfor this process are bis(2-ethylhexyl) hydrogen phosphite and isooctylacid orthophosphate, the latter being a commercially available mixtureprincipally of monoand diisooctyl acid orthophosphate.

In carrying out the process of this invention, a polymer as produced by:the aforedescribed polymerization processes or others well known in theart and which is contaminated with metal-bearing catalyst residues canbe contacted with the phosphorus ester prior to the filtration or otherseparation of the polymer or subsequent thereto. In both alternate casesthe subject phosphorus ester can be utilized alone or in combinationwith other washing or solubilizing agents such as alkanols.

Generally a sufficient amount of the selected phosphorus ester isemployed to insure a substantially complete treatment of the heavy metalcatalyst residues in the polymer. The amount of the ester utilized isgenerally small, i.e. in the range of about 0.5 to moles per equivalentof total catalyst and cocatalyst, and preferably about 1 to 3 moles,i.e., for a mixture of 1 mole of triethylaluminum and 1 mole of TiC1from 3 to 60 moles and preferably from 6 to 18 moles of ester.

Separation of the solubilized catalyst residue from the polymer isreadily accomplished either before or after precipitation of thepolymer. For example, the phosphorus ester can be introduced into asolution of polymer in an inert liquid hydrocarbon containing thecatalyst residues to react with the catalyst residues to form a complexwhich is miscible with the polymer solution. Temperatures ranging fromabout 95 to 250 C. are ordinarily required to maintain the polymer andsolubilized catalyst residues in solution. Sufficien-t positive pressureis required to maintain the components of the solution in the liquidphase; pressures in the range of p.s.i. to 3000 p.s.i. have been foundto be particularly satisfactory. The solution is then contacted underthe above mentioned conditions with an absorbent capable of selectivelyadsorbing the solubilized catalyst residues. Suitable adsorbants includesilica, alumina, fullers earth, and bauxite. Following treatment withthe adsorbent, the polymer, now substantially free of contamination bycatalyst residues, may be isolated by precipitation, as by cooling oraddition of a suitable non-solvent, e.g. an alcohol. Such as methanol,ethanol, n-propanol, is-opropanol, n-butanol, etc., followed byfiltration.

When the solubilized catalyst residues are separated from the polymersubsequent to the precipitation of the polymer, the mixture of polymerand catalyst residues may be treated with the phosphorus ester when thepolymer is in solution in an inert liquid hydrocarbon solvent, asaforedescribed, or when it is present as a slurry in a hydrocarbondiluent. It is generally convenient although not necessary to performthese treatments using the same hydrocarbons employed during thepolymerization step. When treating the polymer 'as a slurry, it ispreferred to increase contact between the contaminated polymer and theester by vigorous agitation or stirring. Treatment of the polymer as aslurry is not restricted to the elevated temperatures and pressuresrequired for treatment of the polymer in solution. For example, suchtreatment may be effected at room temperature and atmospheric pressure,if desired, although it is preferable to carry out the treatment in therange of about 40 to 80 C. Precipitation of the treated polymer may becompleted by adding an excess of a non-solvent for the polymer, such asan alkanol. Alternatively, the ester may be introduced concurrentlywith, or in admixture with, the non-solvent to carry out precipitationand catalyst removal in one step.

The resultant precipitate of polymer may then be separated byfiltration, centrifugation, or the like from the polymer solvent whereinis contained substantially all of the catalyst residues in solubilizedform. After separation, the solid polymer, which is substantially freeof catalyst residues, may be further washed with an alcohol or acid,such as hydrochloric acid, dried, compacted and packaged.

The invention will be more fully understood by reference to thefollowing illustrative examples. In Examples I and II the polymerizationwas carried out in a 500- ml. three necked Morton flask modified with abottom draw-off, a side tube for injecting catalyst solutions through arubber serum cap, and a thermocouple well. The flask was equipped with aheating mantle, a mechanical stirrer, a solvent inlet, a propyleneinlet, a mercury mon-ometer and a vent. The propylene pressure wasmaintained at 60 mm. Hg (gage) in the reactor by means of a reducingvalve in the propylene line.

Example I In the reactor was placed 250 ml. purified decalin. Thedecalin was heated to C. and then saturated with propylene. 6.5 ml. of a0.5 M solution of triethylalurnimum in purified decalin was injectedfollowed by 6.5 ml. of a 0.5 M suspension of TiCl in decalin (the TiClhad been ground with steel balls in decalin prior to use).Polymerization started at once and was continued for 20 minutes,maintaining the reactor temperature at 100 C. and the reactor pressureat 60 mm. Hg (gage).

The contents of the reactor were then transferred without delay toanother flask similar to the above-described reactor, under a N blanket.15 ml. of bis(2-ethylhexyl) hydrogen phosphite was added. The resultantsolution was allowed to cool, gradually with stirring, to roomtemperature. During this period the polymer precipitated. Thedecalin-polymer slurry was then removed from the bottom of the secondflask into a covered, N -blanketed sintered glass filter. The whitepolymer was collected, washed with 250 ml. of cold purified decalin, anddried in vacuum at 60 C. 15.8 g. of white, solid polymer was isolated.The ash content of the dried polymer was 0.10% by Weight.

In contrast, a second polymerization carried out exactly as that above,except that the addition of a solubilizing agent was omitted, uponabsorption of 17.6 g. of propylene yielded 16.7 g. of a dried polymerhaving an ash content of 1.57 weight percent. Before drying the polymerwas a deep purple; after drying, it was white.

Example [I The procedure of the first polymerization of Example I wasrepeated except that'15 ml. of isooctyl acid orthophosphate was added asthe catalyst solubilizing agent. The ash content of the resultantpolymer was 0.08% by weight.

Example 111 To an agitated polymerization reactor of a continuous systemwere charged 250 lbs. per hour of cyclohexane, 25 lbs. per hour ofethylene, 4.4 lbs. per hour of propylene, .071 lb. per hour of a 9:1 byweight mixture of titanium tetrachloride and vanadium oxytrichloride,and 0.12 lbs. per hour of aluminum triethyl. A temperature of 221 C. anda pressure of 1900 p.s.i. were maintained during the reaction. Theresultant polymer solution was mixed with a 15 weight percent solutionof isooctyl acid orthophosphate in cyclohexane at a rate of 21.8 lbs.per hour. This solution, containing approximately 3.5 weight percent ofpolymer, was then passed through a 72" absorption column having adiameter of 8" and containing lbs. of 16 to 20 mesh activated bauxite(Florite, Floridin Co.) at the rate of 330 lbs. per hour. Columntemperature was 220 C. and column pressure 1900 p.s.i. during theabsorption.

The solvent was flashed off and molten ethylene-propylene copolymerrecovered which exhibited a melt index of 0.90 and an inorganic ashcontent of 83 parts per million.

As seen from the above examples, the phosphorus esters are effective inreducing the ash content of commercially important low pressure olefinpolymers. Furthermore, only small amounts of the esters are required,and the esters are readily available in commercial quantities and arerelatively inexpensive.

This invention is not intended to be limited to the specific exampleswhich have been presented merely as illustrations. Modifications andvariations may be made without departing from the scope of theinvention.

What is claimed is:

1. A method of removing ash from a normally solid, polymerized olefinproduct prepared with a heavy metal catalyst formed by admixing (a)strong reducing agent selected from Group I-A, II-A and III-A metals,metal alkyls, metal alkyl hydrides, metal alkyl halides and mixturesthereof, and (b) a halide of a metal selected from Group IV-B, V-B andVI-B which comprises contacting the polymerization product containingpolymer and catalyst residues with a minor amount, suflicient tosolubilize the catalyst residues, of a treating agent consisting of aphosphorus ester corresponding to the formula wherein R is selected fromthe group consisting of alkyl radicals containing from 1 to about 20carbon atoms and aryl radicals, R is selected from the group consistingof hydrogen, alkyl radicals containing from 1 to about 20 carbon atoms,and aryl radicals, and X is selected from the group consisting ofhydrogen and hydroxyl radical, and separating the solubilized residueand the phosphorus ester from the polymer. 5

2. The method of claiml wherein R contains from 6 to about 10 carbonatoms, R is from the group consisting of hydrogen and alkyl and arylradicals of from 6 to about 10 carbon atoms.

3. The process of claim 1 in which the phosphorus ester is utilized inan amount of from about 0.5 to 10 moles per equivalent of catalystemployed.

4. The method of claim 1 in which the temperature of contacting is about20 to 250 C.

5. The method of claim 1 in which the polymerized product ispolypropylene.

6. The method of claim 1 in which the polymerized product ispolyethylene.

7. The method of claim 1 in which the polymerized product is anethylene-propylene copolymer.

8. The method of claim 1 in which the phosphorus ester isbis(Z-ethylhexyl) hydrogen phosphite.

9. The method of claim 1 in which the phosphorus ester is isooctyl acidorthophosphate.

1 The et d o m n hich t e p yp p e is prepared in the presence of acatalyst formed by admixing an aluminum alkyl with a titanium salt.

11. The method of claim 6 in which the polyethylene is prepared in thepresence of a catalyst formed by admixing a titanium salt, an oxyhalideof vanadium, and an aluminum alkyl.

12. The method of claim 1 in which the polymer is precipitated prior tothe separation of the solubilized catalyst residue.

13. The method of claim 1 in which the solubilized catalyst residue isseparated from a solution of polymer containing the catalyst residue bycontacting said solution and solubilized catalyst residues with anadsorbent which selectively adsorbs said solubilized catalyst residues.

14. The process of claim 13 in which the contacting is carried out at atemperature in the range of to 250 C. and at a pressure in the range of15 to 3000 p.s.i.

15. A method of removing ash from normally solid polymerized alphaolefin product prepared in the presence of a catalyst containing apartially reduced titanium halide and an aluminum alkyl compound whichcomprises contacting the polymerization product containing polymer andcatalyst residues with a minor amount, sufficient to solubilize thecatalyst residues of a treating agent consisting of a phosphorus esterselected from the group consisting of bis(2-ethylhexyl) hydrogenphosphite and isooctyl acid orthophosphate and subsequently separatingthe solubilized catalyst residue and the phosphorus ester from thepolymer.

16. The method of claim 15 in which the titanium halide is titaniumtrichloride and the aluminum alkyl compound is aluminum triethyl.

17. A method of removing ash from normally solid polymerized alphaolefin product prepared in the presence of a catalyst containing atitanium halide, an oxyhalide of vanadium, and an aluminum alkylcompound which comprises contacting the polymerization productcontaining polymer and catalyst residues with a minor amount, sutficientto solubilize the catalyst residues of a treating agent consisting of aphosphorus ester selected from the group consisting of bis(2-ethylhexyl)hydrogen phosphite and isooctyl acid orthophosphate and subsequentlyseparating the solubilized catalyst residue and the phosphorus esterfrom the polymer.

18. The method of claim 17 in which the titanium halide is titaniumtetrachloride, the oxyhalide of vanadium is vanadium oxytrichloride andthe aluminum alkyl compound is aluminum triethyl.

References Cited by the Examiner FOREIGN PATENTS 12/1957 Germany.

2/1958 France.

1. A METHOD OF REMOVING ASH FROM A NORMALLY SOLID, POLYMERIZED OLEFINPRODUCT PREPARED WITH A HEAVY METAL CATALYST FORMED BY ADMIXING (A)STRONG REDUCING AGENT SELECTED FROM GROUP I-A, II-A AND III-A METALS,METAL ALKYLS, METAL ALKYL HYDRIDES, METAL ALKYL HALIDES AND MIXTURESTHEREOF, AND (B) A HALIDE OF A METAL SELECTED FROM GROUP IV-B, V-B ANDVI-B WHICH COMPRISES CONTACTING THE POLYMERIZATION PRODUCT CONTAININGPOLYEMR AND CATALYST RESIDUES WITH A MINOR AMOUNT, SUFFICIENT TOSOLUBILIZE THE CATALYST RESIDUES, OF A TREATING AGENT CONSISTING OF APHOSPHORUS ESTER CORRESPONDING TO THE FORMULA
 6. THE METHOD OF CLAIM 1IN WHICH THE POLYMERIZED PRODUCT IS POLYETHYLENE.